The present invention relates to Reed-Muller decoding apparatus and decoding method.
Reed-Muller code is known as a kind of error correction code. An ordinary Reed-Muller code is (32, 6) Reed-Muller code for converting 6-bit information data into a 32-bit code word. For the Reed-Muller code, it is known that, suppose n=2m (n is a code length, m is a natural number (if n=32, m=5)), the minimum Euclidean distance between code words is 2m-r (r is an order of code). In general, if the minimum Euclidean distance between code words is longer, the error correction code has better performance (resistant to errors). However, the longer the minimum Euclidean distance, the lower the transmission rate or coding efficiency. Therefore, in order to improve the performance of the Reed-Muller code without greatly lowering the transmission rate, a method is proposed to increase the minimum Euclidean distance by adding mask symbols to the conventional Reed-Muller code (3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Multiplexing and channel coding (FDD) (Release 1999) 3G TS 25.212 V3.3.0 (2000-06). This code is called “(32, 10) Reed-Muller code” for converting a total 10-bit information data where 4-bit mask symbols are added to a 6-bit information data into a 32-bit code word.
It is known that the Reed-Muller code decoding apparatus can be realized by a simple majority decision circuit (Jpn. Pat. Appln. KOKAI Publication No. 9-74359). The majority decision circuit for (32, 6) Reed-Muller code can be realized relatively easily. However, for (32, 10) Reed-Muller code, it is difficult to calculate the checksum to be determined for the majority decision.
As an example of decoding without using a majority decision circuit, a maximum likelihood decoding by calculating a correlation value is known (Harmonization impact of TFCI and New Optimal Coding for extended TFCI with almost no complexity increase (rev 1) TSGR #6 (99) 970). However, calculating the correlation of all code words for a received coded signal, essentially, operation load is high in this method, increasing the hardware scale; therefore, this method is difficult to realize for (32, 10) Reed-Muller code.
As mentioned above, it has been difficult to realize the decoding apparatus for recently proposed Reed-Muller code containing mask symbols which is resistant to the error.